<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
<script>
    // while()只要小括号里的条件为真，就会一直输出
    // 输出0~3
    var a=3;
    while(a<=10){
        alert(a);
        a++;
    }
</script>    
</body>
</html>